Senior Java Developer Interview Questions series-5 OOPs, Core Java 8, Spring, Coding,prep material Medium

The questions will revolve around the basic, core & advanced fundamentals of Java. OutOfMemoryError is the subclass of java.lang.Error which generally occurs when our JVM runs out of memory. Finalize is used to perform clean up processing just before the object is garbage collected. Sometimes, a thread goes to the waiting state, where it remains idle because another thread is executing. When the other thread has finished, the waiting thread again comes into the running state. Within the run() method, you must specify the thread’s code.

java developer interview questions

Contiguous memory locations are usually used for storing actual values in an array but not in ArrayList. Java is called platform independent because of its byte codes which can run on any system irrespective of its underlying operating system. In case you attended any Java interview recently, or have additional questions beyond what we covered, we encourage you to post them in our QnA Forum. As a Java professional, it is essential to know the right buzzwords, learn the right technologies and prepare the right answers to commonly asked Java Interview Questions. Here’s a definitive list of top Java Interview Questions that will guarantee a breeze-through to the next level.

Q How objects of a class are created if no constructor is defined in the class?

If a child class inherits the property from multiple classes is known as multiple inheritance. Compile time polymorphism is method overloading whereas Runtime time polymorphism is done using inheritance and interface. When a method is declared final then it can’t be overridden by the inheriting class. Java doesn’t use pointers because they are unsafe and increases the complexity of the program. Moreover, since JVM is responsible for implicit memory allocation, thus in order to avoid direct access to memory by the user,  pointers are discouraged in Java. The length() method of String class doesn’t return accurate results because it simply takes into account the number of characters within in the String.

In this example, we are going to copy the values of one object into another using java constructor. However, we can copy the values from one object to another like copy constructor in C++. Based on the parameters passed in the constructors, there are two types of constructors in Java. There are the following basic differences between the object-oriented language and object-based language.

Is it possible to import the same class or package twice in Java and what happens to it during runtime?

They are useful for performing initialization of complex static objects or to register a type with a static registry, as JDBC drivers do. Sleep() is most commonly used for polling, or to check for certain results, at a regular interval. Wait() is generally used in multithreaded applications, in conjunction with notify() / notifyAll(), to achieve synchronization and avoid race conditions.

  • There are the following basic differences between the object-oriented language and object-based language.
  • The control of the program post System.exit(0) is immediately gone and the program gets terminated which is why the finally block never gets executed.
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  • However, if you try to do so, the compiler will show an error.
  • Wrapper classes convert the Java primitives into the reference types (objects).

It is because there are chances that the class definition doesn’t exist, and we get the class name from runtime. In the linked list, we only need to adjust the references when we want to delete the element from either end or the front of the linked list. So to manage proper indexing, we need to adjust the values from the array So this adjustment of value is costlier than the adjustment of references. Here in the above snippet, the method testExceptionDivide throws an exception. So if the main method is calling it then it must have handled the exception. Otherwise, the main method can also throw the exception to JVM.

Q In java, how we can disallow serialization of variables?

In Java, the final keyword is used as defining something as constant /final and represents the non-access modifier. Copy Constructor is the constructor used when we want to initialize the value to the new object from the old object of the same class. Go through all the questions to enhance your chances of performing well in the interviews.

Whenever you create the instance of the subclass, an instance of the parent class is created implicitly which is referred by super reference variable. The super() is called in the class constructor implicitly by the compiler if there is no super or this. Reflection is a runtime API for inspecting and changing the behavior of methods, classes, and interfaces. Java Reflection is a powerful tool that can be really beneficial. Java Reflection allows you to analyze classes, interfaces, fields, and methods during runtime without knowing what they are called at compile time.